Method for effecting ore flotation



United States Patent j 3 355,017 METHOD FOR EFFlllCTlNG ORE FLOTATION Vernon Paul Wystrach, Noroton Heights, and Michael McKay Rauhut, Norwalk, Conn., and Wilfred Lawson Freyberger, Houghton, Mich., assignors to American Cyanamid Company, Stamford, Conn., a corporation of Maine No Drawing. Filed Dec. 2, 1966, Ser. No. 598,597 Claims. (Cl. 209-166) ABSTRACT oF THE DISCLOSURE A promoter which in aqueous solution ionizes to give a dithiophosphinate ion and which has been found to be particularly effective for the flotation of middling particles of base metal sulfide ores.

This application is a continuation-in-part of our copending application for United States Letters Patent, Ser. No. 328,490, filed Dec. 6, 1963. v

The present invention relates to the beneficiation of sulfide ores containing middling particles for the recovery of mineral values therein. More particularly, it relates to a process of flotation in which a sulfide ore containing a substantial amount of middling particles is floated in the presence of a promoter or collector compound which in aqueous solution ionizes to give a dithiophosphinate ion of the formula:

where each R represents an alkyl group from 2 to 12 carbon atoms, floating ofl a concentrate enriched in metal values and containing metal-bearing middling particles, and rejecting precipitated tailings poor in mineral values.

The compounds hereinabove defined may be utilized as the free acid, or a salt thereof, such as the ammonium, sodium, potassium or calcium salt as a promoter or collector in the ore flotation treatment of sulfideo-res in which middling particles comprise a major proportion of the ore to be treated. I U

As is known, middling particles which result from either coarse grinding or from intimate association of the component minerals which make up an ore and frequently exist even after fine grinding are composed of two or more mineral species. In general, such polyphase particles are generally more difficult to concentrate by no: tation than free mineral grains. InLsome free-milling ores, the values are readily separated from the gangue by crushing and grinding and floating to permit the application of flotation techniques. In other ores a middling treatment problem is presented. The extractive metallurice gist is thus compelled to compromise 'between obtaining a desired high recovery of mineral values and the grade of the concentrate produced. High recoveries in concentrates of low grade entail high treatment costs in subsequent upgrading and refining operations, which may force the' rejection of larger percentages of the contained metal values so as to obtain a concentrate which is salable or amenable to further treatments. Further, in many cases, the middling particles are not recovered, even though amenable to standard refining processes, and thus represent high losses of the desired mineral values.

The dithiophosphinate promoters hereinabove defined surprisingly provide a means of solving this vexing middling treatment problem. Moreover, these promoters aremore eflective than known collectors usually employed in floating coarse mineral particles, particularly particles in the plus 150 Tyler mesh range. This property affords the possibility of treating larger tonnages of ore in a concentrating plant through the decrease of the fineness of grind Without sacrificing metal recovery from the ore.

In general, it has been observed that a coarser grinding gives good recovery and where only a comparatively small portion of the metal sulfides are exposed, still the promoter is sufficiently powerful to cause particles having such mineral value to float. Hence, a much coarser grind may be used, without loss of valges to the rougher tailings, permitting a major reduction in the grinding costs. Some ores are fairly readily ground; others are less amenable toward grinding and fine grinding involves considerable power; time and equipment are costly. It is found that by employing the dithiophosphinates of the present invention larger particles having a smaller proportion of sulfide ore value may be floated. As a result a rougher concentrate orfirst float is obtained containing a larger percentage of the total mineral values than has been possible with prior art procedures.

The middlings, in this rougher concentrate, may be then reground and, thus,- only a comparatively small portion. of the total quantity of ore must be reground to separate the mineral values from the gangue. A secondary, cleaner float may then be made in which the ore particles are separated from any gangue as the particles are then all fairly small, the particles of ore have less gang'ue attached, and a high grade of concentrate is obtained.

As the cost of grinding ores, such as copper, lead, zinc, lead-zinc, copper-molybdenum, cobalt or nickel, is an appreciable and important part of the milling cost, the reduction in grinding requirements without loss of grade or value in the final product is a distinct commercial advantage. Usually, it is found that there is less loss in the flotation tailings than with the conventional promoters. Even though the losses in the tailings are usually only of the order of between five and twenty percent of values in the ore, reduction in these losses is extremely important. For instance, large copper operations may mine and beneficiate as much as 50,000 tons of ore a day. Thus, a small percentage increase in recovery which may be ac complished without additional costs is highly attractive.

Advantageously, the dithiophosphinate promoters exhibit enhanced selectivity between sulfides of the base metals, such as copper, and the sulfides of iron, such as iron pyrites. This selectivity is a vital factor in the differential flotation of copper and iron sulfides as well as in the separation of other mixed sulfide ores into their valu- 3 able components by flotation, permitting the production of flotation concentrates of higher metal content and lowering of refining costs.

In general, when employing the dithiophosphinate prometers or collectors, it is a good practice that flotation be carried out in an alkaline pulp environment whose pH value range is between about and 12.5. However, these collectors have been found to be far more effective at pH values between about 7 and less than about 10 than conventional collectors. As such, they can conveniently be employed under less alkaline conditions, although with some loss of efficiency as compared to their behavior at higher pH values.

The dithiophosphinates of the present invention, individually or in admixture, may be used as the sole promoters for a particular ore. Alternatively, they may be employed in combination with commonly used promoters, such as alkali metal, xanthates, clithiophosphates, mercaptobenzothiazole derivatives, substituted thioureas, xanthoyl formates, xanthate esters and alkyl thionocarbamates.

The promoters of the present invention can be prepared in a straightforward manner as set forth in United States Letters Patent No. 3,238,248 wherein secondary phosphine, sulfur, water and a base, such as ammonium hydroxide, are reacted to produce the salt of a secondary dithiophosphinic acid. These salts can be readily converted to the corresponding acids, esters or other salts, if desired. Generically, the dithiophosphinate promoters or collectors contemplated herein are:

wherein X is represented by the substituent wherein Y represents hydrogen, ammonium, substituted ammonium, alkali metal, such as lithium, potassium or sodium, an alkaline earth metal, such as calcium; and R through R may be the same or different aliphatic hydrocarbon from 2 to 12 carbon atoms.

The following examples demonstrate the utility of the dithiophosphinates as flotation promoters. In certain of the examples, the dithiophosphinates are compared to promoters currently in regular plant use on specified ores. Such regular usage was established after comparative testing of known promoters to permit selection of a promoter which up to the present time give optimum recovery of values in the flotation of the specified ores.

Example 1 A Mexican copper ore was ground to minus 48 mesh in particle size. Two flotation tests were conducted on representative portions of this ground ore. In Test 1, the ore was floated with 5.0 lb./ton lime, 0.2 lb./ton pine oil as frother and 0.023 lb./ton of sodium diisobutyldithiophosphate as promoter. This procedure represented standard plant practice on this copper ore. In Test 2, the ground ore was treated by an identical flotation procedure as in Test 1 except that 0.023 lb./ton of ammonium diisobutyldithiophosphinate was employed as flotation promoter. Copper concentrates were removed over a period of 9 minutes, were screened, infrasized and analyzed for copper to permit the calculation of the total percentage of copper floated from each size fraction as given in Table 1, below.

Microscopical examination indicated that middling par ticles exist in all mesh size fractions listed in the said table as well as in each of the tables presented in the examples below.

TABLE I Particle Size Percent Copper Floated Minus Plus Test 1 Test 2 48 mesh 65 mesh 295 microns" 208 micil-ons. i 8 8 05 mesh..- mes 1. 08 micgpns 147 miciy'im i 5 100 mes mes 147 micrhons 104 micigins. i 86 3 150 mes 200 mes 104 micrrfnsu 74 cmlrons. 0 0 200mm 74 micr ons.-. 56 microns. 8 6 56 microns. 40 microns 89. 8 90. 4 40 microns. 28 microns 89. 5 89. 5 28 microns. 20 microns 85. 1 85. 1 20 microns. 14 micron 70. 3 79. 3 14 microns.. 43. 2 47. 3

Overall Copper Recovery (Percent). 80. 7 83. 3

The dithiophosphinate promoter gave generally higher copper recoveries in the coarser sizes than were obtained with the dithiophosphate promoter. Also the total copper recovery was higher with the dithiophosphinate promoter. Microscopical examination of the various concentrates indicated that the increase in copper recovery was due to the flotation of a higher percentage of middling particles when the dithiophosphinate was employed as the flotation promoter.

Example 2 A copper ore from the Western United States was ground to minus 65 mesh and floated in the presence of 2.0 -lb./ton lime, 0.05 lb./ton cresylic acid as frother and 0.12 lb./ton of promoter. In two separate tests on representative samples on this ground ore, sodium diethyldithiophosphate (Test 1) and ammonium diisobutyldithiophosphinate (Test 2) were used as the respective promoters. The flotation operation was conducted for a period of 5 minutes and copper concentrates were produced which were screened, infrasized and assayed for copper. This technique permitted the determination of copper recoveries in various size ranges as shown in Table II, below.

From the above table, it will be noted that the copper recovery in most of the size ranges as well as the overall copper recovery was higher when utilizing ammonium diisobutyldithiophosphinate promoter in contradistinction to the use of sodium diethyldithiophosphate, the standard plant promoter. Further, microscopical examination of the various concentrates indicated that this increase in copper recovery was generally due to the flotation of a higher percentage of middling copper grains in the pres ence of the dithiophosphinate promoter.

Example 3 Two flotation tests were conducted on a South American copper ore which was ground to minus 48 mesh in particle size in the presence of 2.75 lb./ton lime. In Test 1, the ground ore was floated with 0.02 lb./ton of the methyl ether of polypropylene glycol as frother and a.

mixture of :04 lb./ton of sodium isopropyl xanthate and 0.01 lb./ ton of Sodium diisopropyldithiophosphate as promoters In Test 2, a second sample of this ore also was floated by the identical procedure except that 0.05 lb./ton of ammonium diisobutyldithiophosphinate was substituted for ammonium diisopropyldithiophosphate. The resulting copper concentrates were screened, infrasized and the various size fractions assayed for copper. The copper recovery in each size fraction is set forth in Table III, below.

TABLE III Particle Size Range Percent Copper Floated Minus Plus Test 1 Test 2 65 mesh 3 s3. 2 86.6 1 0 mes 147 mimfimi ss. 4 as. e 150 mes 7 104 miclgmiu 87.3 90.3 200 mes 74 microns 88.9 90. s 74microns slam-nan 56 microns. 40 microns 85. 6 87. 3 40 mierons 28 microns 86. 5 86. 5 28 microns 14 microns 83. 5 84. 6 14 microns microns. 75.6 75.6 10 microns 57. 7 55.6

Total Copper Recovery (percent).... 82. 5 84.2

In substantially all of the fractionsfrom the flotation operation employing the ammonium diisobutyldithiophosphinate as promoter, the copper recovery Was higher than obtained with the known promoter combination.

Example 4 A South American copper ore (1 6% copper) was ground at 55% solids in Water to minus65 Tyler mesh in the presence of 5.0 lb./ton of calcium oxide. The

ground ore was then diluted to 22% solids in a laboratory Fagergren flotation machine. The pH of the pulp was 11.5-11.7. The pulp was conditioned with a,collector and a frother and floated for 5 .minutes. The collector dosage was 0.08 lb./ton and the frother, a 1:1 mixture by volume of pine oil and a polypropylene glycol ether, was added in the amount of 0.091 lb./ton. Two flotation tests were run by this method. Test 1 employed as promoter 0.06 lb./ton of sodium isopropyl xanthate and 0.02 isopropyl ethylthionocarbamate. Test 2 used 0.08 lb./ton of ammonium isobutyldithiophosphinate as promoter in lieu of the promoter utilized in Test 1.

The recovery of copper obtained in these tests as a function of particle size is given in the following Table IV:

TABLE Iv Percent Recovered Tylermesh w Test 1 Test 2 Plus 150 150/325 l Minus 325 Overall Cu Recovered (percent) Alkali metal and alkaline earth metal salts of the dithiophosphinates are effective promoters as" indicated by the following copper recoveries obtained in flotation tests on the same ore and by the same method as described for Test 2 in Example 4. In this series of tests the promoter used was a diisobutyldithiophosphinate as the free acid or 1n the form of various salts as set forth in Table V below.

A variety of dialkyl (C to C dithiophosphinates as ammonium salts defined generically hereinabove were used as promoters on the same ore and by the same meth ed as described in Test 2 of Example 4 with the following copper recoveries and concentrate grades:

TABLE VI Promoter Concentrate Percent Cu Grade (Per- Reeovered cent Cu) Alkyl Group LbJTon' /ii /.P\H C-C3H1-1 NH S (ll-0 C3H7-i Example 7 A second South American copper sulfide ore (1.5% Cu) containing chalcocite as the chief copper mineral is ground at 60% solids in water to minus 65 Tyler mesh, in the presence of varying amounts of calcium oxide, leading to the pH values of the flotation pulps as listed in Table VII below. This ground ore was then treated in the". same manner, in every essential respect, as described in Test 2 of Example 4 employing ammonium salt of diisobutyldithiophosphinic acid in varying amounts. The

v A copper sulfide ore from Utah (0.90% Cu), containing chalcopyrite as the principal copper mineral, is ground at 59% solids in Water to minus 65 Tyler mesh in the presence of 2.00 lb. Ca. (OH) /ton and 0.05 lb. sodium cyanide per ton..The ground ore is diluted to 18% solids in a' laboratory Fagergren cell. To this pulp 0.022 lb./ton of the ammonium salt of diisobutyldithiophosphinic acid is added with stirring. Then 0.013 lbl/ ton of frother, pine oil, is added and conditioning continued 1 minute. The ore is then floated for 2 minutes, at which point 0.013 lb./ ton of pine oil is added and conditioned 30 seconds. Flotation is then continued for 3 minutes and the total concentrates combined. This total concentrate contains 91.2% of the copper in the flotation feed at a concentrate grade of 17.8% Cu.

Example 9 An African ore containing both sulfide and oxide copper (4.2% sulfide C-u, 3.4% oxide Cu) is ground at 65% solids in water to minus 65 Tyler mesh. The ground ore is then diluted to 22% solids in a laboratory Fagergren flotation machine. The pH of the pulp is 8.9. To this pulp 0.19 lb./t on of the ammonium salt of diisobutyldithiophosphinic acid is added and conditioned for four minutes. Then, 0.07 lb./ ton of methyl amyl alcohol as frother is added and conditioned for one minute longer. The ore is floated for five minutes to make a sulfide copper concentrate. To the pulp remaining in the cell is added 1.1 lb./ ton sodium hydrosulfide and 0.010 lb./ton of methyl amyl alcohol and the pulp is conditioned five minutes, then floated for 2.5 minutes. Following this flotation, 0.43 lb./t on of sodium hydrosulfide is added and the pulp is conditioned one minute, then floated 2.5 minutes. Then 0.43 lb./ ton sodium hydrosulfide and 0.07 lb./ ton methyl amyl alcohol added and conditioned four minutes. Flotation is carried out for four minutes longer. The final pH is 9.1. The last three concentrates are combined as an oxide concentrate. The results of flotation are in the table below:

Example 10 A Missouri copper-lead ore (2.3% Pb, 0.36% Cu) is ground to minus 48 Tyler mesh in the presence of 0.04 lb./t-n sodium isopropyl xanthate and 0.05 lb./ton sodium sulfide. Then 0.015 lb./ton of the ammonium salt of diisobutyldithiophosphinic acid is added to the ore pulp in the flotation cell along with 0.09 lb./ton of frother (a mixture of two parts of secondary heptyl alcohol with one part creosote). Flotation is commenced immediately and continued for minutes to make a combined copperlead coarser concentrate. The pH of the flotation pulp is 8.3. The concentrate assays 47.9% Pb and 7.2% Cu, and contains 96.3% of the lead and 92.0% of the copper originally present in the ore.

Example 11 A Missouri lead-zinc sulfide ore (0.94% Pb, 5.3% Zn) is ground at 60% solids in Water to minus 65 Tyler mesh in the presence of 0.050 lb./ton sodium cyanide. The ground ore is then diluted to 22% solids in a laboratory Fagergren flotation machine and the collector and 0.082 lb./ ton of pine oil frother added. The resulting mixture is conditioned for two minutes, after which flotation is carried out for five minutes to produce a lead concentrate. To the pulp remaining in the Fagergren machine, 1.0 lb./ ton of Ca(OH) is added and conditioned for two minutes. Following this, 0.50 lb./ ton of copper sulfate pentahydrate is added and conditioned for five minutes. Then, additional collector is added and conditioned for one minute. Then, 0.082 lb./ ton pine oil is added and conditioned for one minute followed by flotation for five minutes to make a zinc concentrate.

Two tests were conducted using separate additions of 0.05 lb./ ton ammonium diisobutyldithiophosphinate in the 8 lead and Zinc flotation treatments in Test 1 and separate addition of 0.05 lb./ton of calcium cyclohexyl dithiophosphinate in Test 2. The results obtained are summarized in Table IX below.

TABLE IX Test 1 Example 12 A Missouri lead ore (1.9% Pb) is ground at 60% solids with Water to minus 65 Tyler mesh in the presence of 0.02 lb. NaCN/ ton. The ground ore is then diluted to 22% solids in a laboratory Fagergren flotation machine. The pH of the pulp is 8.7. To this pulp 0.05 lb./ton of ammonium diisobutyldithiophosphinate is added and conditioned for two minutes, after which 0.082 lb./ton of pine oil is added and conditioning continued for one minute. The ore is then floated for two minutes to make a lead concentrate which assayed 32.5% Pb and represented a recovery of 94.0% of the lead.

Example 13 Flotation tests were conducted on the same lead ore and by the same procedure as described in Example 12. The use of 0.05 lb./ton of the tertiary butylamine salt of dioctyl dithiophosphinic acid as promoter produced a lead concentrate assaying 35.1% Pb and representing a lead recovery of 94.6%. With 0.05 lb./ton of the isopropyl amine salt of diisobutyldithiophosphinic acid as promoter, 94.1% of the lead was floated as a concentrate assaying 33.7% Pb.

Example 14 A Tennessee zinc ore (6.0% Zn) is ground at 60% solids in water to minus 48 Tyler mesh. The ground ore is diluted to 22% solids in a laboratory Fagergren flotation machine. The pH of this pulp is 9.3. To this pulp is added 1.0 lb. copper sulfate pentahydrate/ton and the pulp is conditioned five minutes. Then 0.10 lb./ ton of ammonium diisobutyldithiophosphinate is added and conditioned three minutes, followed by addition of 0.074 lb./ton of a polypropylene glycol frother with a conditioning period of one minute. The ore is then floated three minutes, at which point 0.074 lb./ton of frother is added and conditioned one-half minute, followed by two minutes of flotation. The resulting zinc concentrate assayed 38.5% Zn and the zinc recovery was 98.6%.

Example 15 Marked selectivity obtainable with dithiophosphinate promoter is diflerential flotation is illustrated in this example.

Determinations are made for iron on the various size fractions in the concentrates set forth in Example 3 above utilizing the promoters therein. Such determinations or analysis for iron permitted the calculations of the percentage of iron floated along with the copper in each size fraction as presented in Table X, below.

TABLE X Percent Iron Floated- Example 3 Size Fraction 1 Test 1 Test 2 100 mesh/150 mesh 150 mesh/200 mesh 200 mesh/56 miorons 56 microns/40 microns. 40 microns/28 microns 28 microns/14 microns 14 microns/ microns -10 microns From the above, it can be seen that the iron recoveries generally were considerably lower utilizing the dithiophosphinate promoter than with the known promoter combination.

What is claimed is:

1. In a process for beneficiating base metal ores containing a major amount of middling particles by subjecting said base metal ore as a pulp to froth flotation, said pulped ore being selected from the group consisting of copper sulfides, zinc sulfides, lead sulfides, iron sulfides and mixtures thereof, the improvement which com- 25 prises: incorporating in said pulped base metal ore a dithiophosphinate promoter having the formula:

wherein Y represents a member selected from the group consisting of H, ammonium, alkali metal, and alkaline earth metal; and each R represents an alkyl group having 10 2 to 12 carbon atoms or a lower cycloalkyl; and floating 013? an enriched concentrate containing middling particles of desired metal values.

2. The process according to claim 1 wherein the pro- 5 moter is the ammonium salt and the flotation is carried out in a pH range of 10 to 12.

3. The process according of claim 1 in which the promoter is ammonium diisobutyldithiophosphinate.

4. The process according to claim 1 in which the promoter is sodium diisobutyldithiophosphinate.

5. The process according to claim 1 in which the promoter is calcium dicyclohexyldithiophosphinate.

6. The process according to claim 1 in which the promoter is diisobutyldithiophosphinic acid.

7. The process according to claim 1 in which the base metal ore contains copper.

8. The process according to claim 1 in which the base metal ore contains copper and iron and eflecting separation selectively between said copper and iron.

9. The process according to claim 1 in which the base metal ore contains zinc.

10. The process according to claim 1 in which the base metal ore contains lead.

References Cited UNITED STATES PATENTS 2,206,284 7/1940 Jayne 209-166 X 2,727,067 12/ 1955 Craig 209-166 X 2,797,238 6/1957 Miller 260-500 2,881,200 3/ 1959 Craig 260-500 2,919,025 12/ 1959 Booth 209-166 3,238,248 3/ 1966 Rauhut 260-500 FOREIGN PATENTS 620,135 5/1961 Canada.

OTHER REFERENCES Malatesta, Chem. Abst., vol 41, pp. 2013, 2014 (1947).

HARRY B. THORNTON, Primary Examiner. R. HALPER, Assistant Examiner. 

1. IN A PROCESS FOR BENEFICIATING BASE METAL ORES CONTAINING A MAJOR AMOUNT OF MIDDLING PARTICLES BY SUBJECTING SAID BASE METAL ORE AS A PULP TO FROTH FLOTATION, SAID PULPED ORE BEING SELECTED FROM TEH GROUP CONSISTING OF COPPER SULFIDES, ZINC SULFIDES, LEAD SULFIDES, IRON SULFIDES AND MIXTURES THEREOF, THE IMPROVEMENT WHICH COMPRISES: INCORPORATING IN SAID PULPED BASE METAL ORE A DITHIOPHOSPHINATE PROMOTER HAVING THE FORMULA: 